1. Field of the Invention
This invention relates to flexible shielded or coaxial cables and miniature electrical connectors adapted to receive such cables, and especially to such cable and connector combinations which are adapted to provide excellent conductivity characteristics between the shield of the cable and a terminal in which the miniature connector is received.
2. Discussion of Related Art
Miniature modular connectors have gained great popularity in recent years, especially in communications applications. Cables which terminate in miniature connectors can provide a relatively inexpensive yet highly effective means of interconnecting various components of a modular telephone system. For instance, a telephone base which includes the dialing and the ringing apparatus can easily be attached to a handset by use of a cord terminated by miniature connectors such as a modular plug and modular jack. Miniature connectors have also been found to be very useful in interconnecting the components of computer operated telecommunication terminals and for attaching such terminals through modems to a main communication network.
In order to preserve the integrity of information transmitted through communication data links, it is often necessary to utilize shielded cable. It would be desirable to be able to terminate a shielded cable in a miniature modular connector in order that the advantages of such miniature connectors can be gained by the users of shielded cable. However, certain problems exist with respect to termination of shielded cables which are not present with unshielded cables. For instance, excellent continuity must be maintained from the shield to the terminals of a miniature connector. Also, the shield itself must be suitably adapted to be easily received within a miniature connector. Furthermore, the overall size of the shielded cable must be kept sufficiently small so that the size of the miniature connector itself may also remain small.
To date, little work has been done by others to provide shielded cable and miniature modular connector combinations which are able to perform well at a minimum expense. However, various coaxial cable constructions have been suggested.
For example, U.S. Pat. No. 3,291,891 issued Dec. 13, 1966 to Sharp shows a shielded electric cable which includes a plurality of insulated and uninsulated conductors having the same outer diameter disposed circumferentially along the surface of a center conductor. The conductors are wrapped in a shield which comprises an elongated strip of metal foil which is insulated on one side by a film of suitable material such as polyethylene terephthate resin or the like.
U.S. Pat. No. 3,644,659 issued Feb. 22, 1972 to Campbell shows a cable construction comprising a plurality of twisted pair insulated conductors disposed around a plurality of filler strings. A shield layer is disposed over the twisted pair conductors and is grounded through a drain wire, such as a multi-strand wire which is disposed in the space between two neighboring ones of the twisted pair conductors.
U.S. Pat. No. 3,816,644 issued June 11, 1974 to Giffel et al shows a low noise flexible cord comprising a plurality of insulated conductors which can be disposed around a central core. Some of the conductors are shielded and some conductors are unshielded. The shielded conductors are disposed adjacent uninsulated strands which serve as grounding wires.
Furthermore, various connectors have been suggested in the past. For instance, U.S. Pat. No. 4,054,350 to Hardesty and U.S. Pat. No. 4,160,575 to Schraut show miniature connectors adapted for use with round cable constructions. As described therein, a miniature modular plug is characterized by a unipartite or one-piece rigid dielectric housing having a free end for insertion into a mating modular jack, a movable locking tab extending angularly rearwardly from the free end of the housing and adapted to mate with a tab-receiving latch in the modular jack, a cable input end for receiving a multi-conductor cable having an outer jacket, a terminal receiving side having a plurality of slots for receiving substantially planar contact terminals having insulation-piercing tangs at the lower portion thereof for terminating the conductors of the cable and an upper portion for making electrical contact with the spring contact members of the mating modular jack, and a cable receiving cavity defined by first and second side walls and top and bottom walls for receiving the multi-conductor cable. The Hardesty connector maintains the round cable in a pressurized engagement within an opening by the use of an anchoring member which is hinged to the connector and pivots into the opening. The Schraut connector uses an anchoring member which is separate from the connector and slides into an opening through one wall of the connector.
U.S. Pat. No. 3,751,579 to Nojiri and U.S. Pat. No. 4,195,899 to Radloff et al show strain relief collars for use with electrical cables. The Nojiri collar is adapted for connection to a housing. Pressure of the collar against a cable can be adjusted by selective insertion of a retainer into a bushing. The retainer contains a plurality of ridges which coact with complimentary ridges on the bushing. The collar used in the Radloff et al device is adapted for connection to a round multi-conductor cable and contains an arcuate section on a fastener clamp for engagement with the round cable. Holding pressure against the cable can be adjusted by selective insertion of the fastener into a base.